PROJECT SUMMARY Acute myeloid leukemia (AML) patients have poor outcomes, largely because current therapies fail to eradicate all AML cells, leaving persistent cancer cells that drive relapse. The ability of AML cells to survive therapy is associated with stem cell properties1,2. These primitive AML cells need to be eradicated to achieve durable remissions. During my Ph.D. training with Dr. John Dick, I studied hematopoietic stem cells1,3 which inspired me to specialize in epigenetic regulation of the stem cell state in AML. For my postdoctoral training, I joined the laboratory of Dr. Bernstein, an expert in epigenetics, and developed an innovative technology to map histone modifications in rare cells4. Using this technology, I describe with unprecedented precision how stem cell genes are silenced by histone 3 lysine 27 trimethylation (H3K27me3), a repressive epigenetic modification that is catalyzed by PRC2 and antagonized by KDM6. PRC2 is frequently impaired in AML, leading to enhanced stem cell properties, but the role of the H3K27 demethylase KDM6 is unknown. I discovered that KDM6 promotes AML cell fitness and is upregulated in AML cells with mutations in IDH1/2 (IDHmut), indicating a dependency of IDHmut AML cells on KDM6 function. The objectives of this proposal are to (1) investigate the function of KDM6 using various human AML cell models, (2) evaluate KDM6 as a therapeutic target in IDHmut AML cells, and (3) delineate the mechanism by which KDM6 promotes AML cell fitness by identifying its downstream targets. These studies will uncover a novel epigenetic mechanism that drives AML and lay the foundation for the development of KDM6 inhibitors to facilitate efficient eradication of AML cells, including those that persist through current therapies. Dr. Bernstein is an outstanding mentor with a history of trainees that obtained group leader positions in academia. He is an internationally respected leader in the fields of epigenomics, cancer and development with appointments at the Massachusetts General Hospital (MGH), Harvard Medical School, American Cancer Society and the Broad Institute. The research will be carried out at MGH, a prestigious research institute and medical center that is part of a vibrant community that includes Harvard Medical School, Dana-Farber Cancer Institute, Brigham and Women's Hospital and the Broad Institute, an environment that fosters collaborations and intellectual exchange. A Research Advisory Committee of world-class physician-scientists will provide advice and guidance: Drs. David Scadden, Jon Aster and Andrew Lane. Critical aspects of the research will be completed through collaborations with Drs. Andrew Lane, David Weinstock and Charles Epstein. The K99/R00 award will provide me with the best opportunity to succeed in my career goals. The detailed training plan includes a Research Advisory Committee and development of leadership and mentoring skills that will be invaluable for a successful transition to independence. The R00 phase of the award will allow me to secure an independent position at a top cancer institute and set up an ambitious research program. 1. P. van Galen et al., Nature. 510, 268?272 (2014). 2. P. van Galen et al., under review at Science (see appendix). 3. P. van Galen et al., Cell Stem Cell. 14, 94?106 (2014). 4. P. van Galen et al., Mol. Cell. 61, 170?180 (2016).